Kedem, 31, took the reins of Weiner's improbable candidacy earlier this spring and helped lead him to the front of the pack of candidates seeking to follow Michael Bloomberg as the next mayor of New York.

He was a junior aide on Hillary Clinton's 2008 presidential campaign, where he worked as a field organizer in several primary states. His abrupt departure suggests the inner circle is tightening even more around Weiner and his wife, Huma Abedin.